In many applications, there is a need for a liquid container which can be simply and reliably operated to deliver a small quantity of liquid therefrom, without resulting in deposit of residual liquid in the outlet. In household applications, for instance, there is a need for a liquid dispenser which will deliver small quantities of liquid soap or cosmetic on demand, and remain in clean condition after use. Flexible, squeeze bottles with simple narrow nozzle apertures are commonly used, but such arrangements commonly result in fouled outlet apertures after use over an extended period of time. This is a particular problem with containers of thick, pastey liquids such as liquid soaps, hand creams and other cosmetic preparations.
There is also a need for containers for semi-solid products such as soaps, shaving creams, cosmetic lotions and the like which can be kept in temperature variable environments such as personal bathrooms, showers etc. in an "outlet downward" condition for ease of operation, but which will not drip or leak from the outlet even when subjected to varying environmental temperatures.
There have been proposals in the past for the provision of an air lock between a body of liquid in a container and the outlet conduit from said container, to guard against unwanted liquid leakage therefrom. For example, U.S. Pat. No. 1,127,387 Alger discloses a form of liquid siphon, e.g. for use with automatic flush tanks and liquid meters, in which a temporary liquid seal is formed in the siphon pipe. The inlet end of the siphon pipe is disposed within a liquid-containing tank, and is overlied by a bell-like structure which forms an air lock above the inlet pipe. The liquid seal in the outlet pipe of the siphon prevents admission of air to the discharge leg of the siphon so as to ensure that the siphon catches in a solid stream. As the liquid rises in the tank, air is trapped and compressed in the bell. This has the effect of forcing the water down the U-tube outlet, to start the operation of the siphon.
U.S. Pat. No. 3,797,513 Hazen shows an alternative arrangement of siphon discharge from a flushing tank, in which the inlet to the U-shaped siphon tube within the tank is overlied by an inverted bell structure, forming an air lock at the tube inlet. Water is supplied to the tank from an outside source, to cause the water level in the tank to rise. This traps and compresses air in the bell, and prevents flow of water down the outlet tube until the water level in the tank reaches a pre-determined level. Once this level is reached, water is forced from the U-trap, air is forced out of the bell and the siphon commences operation until the tank is substantially emptied. Then the cycle is repeated, so as to give regular periodic flushing.
U.S. Pat. No. 2,989,215 Willingham discloses a dispenser for a container for liquids. The dispenser includes a spray nozzle, the inlet to which, inside the container, is surrounded by a measuring cup. The liquid may only enter the nozzle from the measuring cup. On inverting the container, the measuring cup is filled with a pre-determined amount of liquid. Then the container is operated, e.g. by squeezing, to discharge the predetermined amount of liquid therefrom. No air lock arrangement is provided in this disclosure.